The present invention disclosed herein relates to a mobile communication system, and more particularly, to a fixed station receiver for a Multi-Input Multi-Output (MIMO) communication system for providing a terminal using a pre-coding matrix that can increase channel capacity, and an uplink adaptation method thereof.
A channel between a transmitter and a receiver is not fixed in mobile communication systems. Accordingly, it is necessary to measure continuously changing a channel state and produce channel information, and recover a distorted transmission signal by referring to the produced channel information in a mobile communication system. Overall operations for producing the channel information are called channel estimation.
For channel estimation, it is necessary to frequently measure a channel between a transmitter and a receiver of a mobile communication system. For channel measurement, the transmitter and the receiver may transmit and receive appointed signals therebetween. By means of transmission and reception of the appointed signals, the receiver can perceive channel information such as an amplitude decrement and a phase transition value. The perceived channel information may be sent to the transmitter by feedback, or may be used as decoding resources to increase the reliability of the received data information. The appointed signals transmitted between the transmitter and the receiver for measurement of the channel are called Reference Signals (RS), Pilot Signals, or Sounding Reference Signals (SRS).
A 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE)-advanced system supports MIMO transmission such as transmission diversity and a spatial multiplexing method. Particularly, in order to satisfy 15 bps/Hz that is a maximum frequency efficiency of uplink, supporting of spatial multiplexing method is necessarily required. According to application of spatial multiplexing, an uplink data channel may transmit two or less codewords for each terminal.
A terminal of a typical LTE system includes one transmission antenna, while an LTE-advanced system may include two or more transmission antennas even in uplink. Accordingly, channel capacity in the LTE-advanced system may be maximized through linear signal processing between a transmitter and a receiver using a matrix product. In this case, the linear signal processing performed in the transmitter is called pre-coding. Technology of providing optimal pre-coding characteristics for maximizing the channel capacity or increasing multiplexing gain in the LTE-advanced system is urgently needed.